UNIVERSITY PARK, Pa. — This year’s unusually wet spring and early summer has led many farmers to store hay that’s wetter than normal, increasing the danger of barn fires, according to an expert in Penn State’s College of Agricultural Sciences.
“Often, farmers have reported they know the hay they are baling is wetter than they’d like, but with additional rain forecast, they are taking a chance, hoping to save a better-quality product versus letting the rain cause the crop to deteriorate in the field,” said Davis Hill, senior extension associate and director of the Managing Agricultural Emergencies program.
“We have seen an increase in barn fires during the past few weeks, at least some of which were caused by hot hay igniting through spontaneous combustion.”
Most farmers strive to bale hay that is field dried to 20 percent or less in moisture, Hill explained. At this moisture content, the baled hay can cure properly and maintain quality.
Some farmers are reporting having to bale their hay at 25 percent moisture. With a moisture content that high, hay under storage conditions will generate more heat than can safely be dissipated into the atmosphere.
“As temperatures rise, dangers of spontaneous combustion increase,” Hill said. “Farmers need to be diligent in checking their hay, especially if they know they baled hay that was wetter than normal. Smoldering hay gives off a strong, pungent odor. This odor is an indication that a fire is occurring. If even the slightest smell is present, farmers should attempt to take temperature readings of the stack.”
Reaching inside a hay stack will give a cursory clue, Hill noted.
“If it feels warm or hot to the touch, that’s a good indication that problems may exist,” he said. “Taking temperature readings of the stack is most important and the only real way of determining how bad the potential fire problem is before flames ignite.”
Infrared thermometers and digital thermometers are accurate, and local fire companies may be willing to come out with thermal imaging cameras to evaluate a situation, Hill pointed out.
“Most would prefer to come out prior to an actual fire event, as a way to help avoid a catastrophic fire,” he said. “A number of fire companies and silo-fire experts also have probes available that producers can borrow to help them monitor a stack of hay.”
“Keeping a watchful eye on heating hay can save your barn or storage building,” Hill said.
Research and experience suggest farmers and firefighters should be aware of several critical temperatures and action steps involving heated hay. These are:
- Temperature 125 degrees Fahrenheit — no action needed.
- Temperature 150 degrees Fahrenheit — entering the danger zone. Temperatures should be checked twice daily. If possible, stacked hay should be disassembled to allow more air to move around heated bales for cooling.
- Temperature 160 degrees Fahrenheit — reaching the danger zone. Temperature should be checked every two hours. If possible, stacked hay should be disassembled to allow more air to move around heated bales for cooling.
- Temperature 175 degrees Fahrenheit — hot spots or fire pockets are likely. If possible, stop all air movement around hay. Alert fire service of a possible hay fire incident.
- Temperature 190 degrees Fahrenheit — remove hot hay. This should be done with the assistance of the fire service. The fire service should be prepared for hay to burst into flames as it contacts fresh air.
- Temperature 200 Fahrenheit or higher — remove hot hay. A fire is almost certain to develop. This should be done with the assistance of the fire service. The fire service should be prepared for hay to burst into flames as it contacts fresh air.
“Checking the temperature of suspected or hot hay can help you make critical decisions. If you see the temperature rising toward the 150 degree range, you might consider moving the hay to a remote location, away from any buildings or combustible material.
“If you have to have a hay fire, it’s better to have it away from your main hay storage or barn. Use caution when moving heated bales, because they can burst into flames when they are exposed to fresh air. Wetting hot bales down before moving them can help control this hazard.”